1. Field of the Invention
The present invention pertains to apparatus for monitoring respiration of an individual. More specifically, the present invention pertains to apparatus for monitoring respiration of a patient being ventilated through the flexible gas reservoir or bag of an anesthesia machine.
2. Description of the Prior Art
A typical anesthesia machine is provided with compressed gas containers, conduits, relief valves, pressure gauges, flow meters and filters. A face mask is connected by a Y-connection to two flexible conduits, one for inhalation and one for exhalation of the patient. Oxygen or other gases may be provided to the patient through the inhalation conduit and carbon dioxide may be exhaled from the patient through the exhalation conduit. The flexible bag or reservoir fills and empties as the patient is being ventilated. The patient can be ventilated by hand, with a mechanical ventilator or by spontaneous respiration. In spontaneous respiration the patient breathes on his own. In respiration by hand, the flexible reservoir or bag is squeezed during inhalation and released during exhalation. With a mechanical ventilator, the reservoir bag is by=passed to an electrical or pneumatic ventilator.
If the person monitoring the respiration of the patient, usually an anesthesiologist, is near the gas reservoir or breathing bag, he/she can tell by visual observation or feel whether or not the patient's lungs are being ventilated in a satisfactory manner. However, it is not always possible to feel or visually observe the flexible gas reservoir or breathing bag.
In a number of cases, it may be necessary for the anesthesiologist to be located some distance from the patient. For example, the anesthesiologist may need to be out of the operating suite while a patient is undergoing general anesthesia for an MRI (magnetic resonance imaging) procedure. The anesthesiologist may be required to be away from the patient undergoing X-ray or CAT-scan examination to whom general anesthesia has been administered to prevent movement of the patient. This may be required for neonates, infants, children and adults, including confused or disoriented patients. Patients undergoing X-ray therapy for tumors and other specifically located tumors may require general anesthesia for absolute non-movement. In these cases, the anesthesiologist would not be allowed to be near the patient. In other situations, intra-operative X-ray therapy may be given directly to tumors in operating rooms, requiring all personnel to leave the operating suite while the patient is under anesthesia for the X-ray therapy treatment.
Of course the primary purpose of monitoring the respiration of a patient is to make sure proper lung ventilation is taking place and that apnea (an arrest of respiration) does not occur. Apnea or unusual respiratory oxygen changes can be due to laryngospasm, bronchospasm, drug, mechanical, or physiologically induced pulmonary changes, cardiac arrest, malposition of the laryngeal mask airway or aspiration.
To detect apnea and other respiratory problems, most patients placed under general anesthesia are presently monitored with a pulse oximeter. The oximeter utilizes a sensor peripherally attached to some part of the patient's anatomy, e.g. finger, toe or ear lobe. When oxygen decreases to an unacceptable level, the oximeter so indicates allowing the anesthesiologist to take measures to restore proper ventilation. However, with administration of oxygen (typically 50% to 100%) during an anesthetic the pulmonary oxygen saturation level may remain high, due to oxygen super saturation, for two or three minutes after apnea or other respiratory problems occur. By the time the oximeter indicates an oxygen problem, the anesthesiologist must move very quickly to correct the problem. If the oximeter is not properly positioned or the anesthesiologist is slow in reacting, a potentially harmful situation may arise.
Obviously, any improvement in recognizing apnea or oxygen problems more quickly would be desirable. If detection of such problems could occur two or three minutes earlier, it might result in reduction of respiratory problems, including possible death.